An ink cartridge that contains liquid ink and an ink jet recording apparatus to which the ink cartridge is exchangeably attached are examples of the above-described liquid storage container and liquid-consuming apparatus, respectively.
The ink cartridge generally has a container main body that is detachably attached to a cartridge-receiving unit of the ink jet recording apparatus. The container main body includes an ink storage chamber that is filled with ink, an ink-supplying hole for supplying the liquid contained in the ink storage chamber to the ink jet recording apparatus, an ink guide path through which the ink storage chamber and the ink-supplying hole communicate with each other, and an atmosphere communicating path for allowing air to flow into the ink storage chamber from the outside as the ink contained in the ink storage chamber is consumed. When the ink cartridge is attached to the cartridge-receiving unit of the recording apparatus, an ink supply needle included in the cartridge-receiving unit is connected to the ink-supplying hole by being inserted therein, so that the can be supplied to a recording head included in the ink jet recording apparatus.
The recording head included in the ink jet recording apparatus controls an operation of ejecting ink drops using heat or vibration. If the ink-ejecting operation is performed when there is no more ink in the ink cartridge and no ink can be supplied, the recording head will break down. Therefore, in the ink jet recording apparatus, it is necessary to monitor the amount ink remaining in the ink cartridge so as to prevent the recording head from operating when there is no ink.
In light of the above situation, an ink cartridge has been developed which includes a liquid remaining-amount sensor that outputs a predetermined electrical signal when the amount of ink remaining in a container main body is reduced to a predetermined threshold, so that a recording head included in a recording apparatus can be prevented from operating after the ink contained in the ink cartridge runs out.
Recently, various kinds of ink cartridges have been suggested which include a liquid remaining-amount sensor having a cavity that functions as a portion of the ink guide path, a vibration plate that defines a portion of a wall surface of the cavity, and a piezoelectric element provided on the vibration plate. The liquid remaining-amount sensor detects the remaining amount of ink on the basis of variation in residual vibration obtained when the vibration plate is vibrated (see, for example, JP-A-2001-146019).
In general, in a known ink cartridge, the ink storage chamber is formed as a rectangular parallelepiped storage space having a substantially flat bottom surface. An ink outlet is formed in the broad, substantially flat bottom surface or at a position near the bottom surface so as to communicate with the ink-supplying hole via the ink guide path.
However, in the ink storage chamber having such a structure, when the amount of ink remaining in the ink storage chamber becomes small, the small amount of ink is spread over a large area in the form of a thin ink layer along the broad bottom surface. Therefore, the fluidity of the ink toward the ink outlet is reduced. Accordingly, even when the ink still remains in the ink storage chamber, an air layer, which occupies a larger space in the ink storage chamber as the ink is consumed, easily comes into contact with the ink outlet. As a result, there is a risk that large air bubbles will be sucked into the ink guide path instead of the ink. In such a case, even when the ink still remains in the ink storage chamber, the liquid remaining-amount sensor determines that the ink has run out because of the air bubbles sucked into the ink guide path. Therefore, the ink remaining in the ink storage chamber cannot be used.
As described above, there is a problem that when the amount of ink remaining in the ink storage chamber is reduced, the fluidity of the ink toward the ink outlet is reduced in the ink storage chamber and the air bubbles are sucked into the ink guide path. This problem more easily occurs when the area of the bottom surface of the ink storage chamber is increased. Therefore, there is a serious problem that as the capacity of the ink storage chamber is increased to satisfy the requirements for mass printing or the like, the amount of ink that is discarded without being used is increased.
In addition, if the remaining-amount sensor once detects the absence of ink due to the air bubbles that flow into the ink guide path and then the ink remaining in the ink storage chamber moves toward the ink guide path and flows into the ink guide path, the remaining-amount sensor detects the presence of the ink again. The detection of presence of the ink after the detection of absence thereof does not normally occur. Therefore, when this phenomenon occurs, the printer determines that the sensor is malfunctioning and stops the operation.